There have been known several drive systems for ejecting ink droplets with use of an ink jet device, such as a pump system, a piezoelectric system, and a thermal system. According to the piezoelectric system, pressure is applied to ink housed in an ink housing unit and an ink droplet is ejected through the nozzle, by application of a voltage signal (drive voltage) to a piezoelectric element provided in the ink housing unit to reversibly expand or shrink the ink housing unit.
In recent years, ink jet devices are applied to, for example, a field of printing appliances for home use. Also, ink jet devices are used in an industrial field where ink droplets need to be precisely ejected on a large-size substrate for a short time period in a manufacturing process of organic EL (Electro Luminescence) devices and so on. In order to eject ink droplets by an ink jet device for a short time period with high precision, it is necessary to increase the number of times of ink droplet ejection per unit time (hereinafter, referred to also as repetition frequency of ink droplet ejection) and improve landing accuracy of an ink droplet to be ejected. To that end, the following technical problems need to be solved.
Since it is difficult to control volume of an ink droplet at present, an ink droplet having volume smaller than a defined volume can be ejected. There is a case where such an ink droplet having the smaller volume tends to fly in various directions through a nozzle, and as a result landing accuracy deteriorates. Furthermore, in the case where a precedent ink droplet, which has volume smaller than the defined volume, adheres near the nozzle and then a subsequent ink droplet comes into contact with the precedent ink droplet, the precedent ink droplet is combined with the subsequent ink droplet, and surface tension thereof deflects a straight flight course of the subsequent ink droplet. This might extremely deteriorate landing accuracy.
In response to these technical problems, Patent Literatures 1 and 2 each disclose a method with use of an ink jet device employing the piezoelectric system for example.